A data transmission network is known to be made up of a plurality of units, generally called terminals or stations. The latter communicate with one another by way of a transmission system that has a physical transmission carrier made up of either two pairs of telephone wires or a coaxial cable or optical fiber cables.
Local area networks are transmission networks limited to a region of limited surface area (building, factory, campus, hospital, etc.), where the distances between stations range from several meters or tens of meters to several kilometers. When this local area network is located in a building, it is increasingly often prewired. This means that all the physical transmission links of the network are installed in the building beforehand, before the users of the building occupy the various places in it.
In general, a prewired building includes a general distributor and a plurality of subdistributors. The subdistributors are the basic elements of the wiring system. It is through them that all the local information processing or office automation links, and those of the switched (telephone) network serving all the offices located within a radius of 200 m around the subdistributor converge. The function this subdistributor performs in the area where it is located is patching. This patching makes it possible to create different links which are needed because of the prewiring of the building. It is generally at the level of the subdistributor that the interconnection with the networks of the higher category, to which the local area network of the building is connected is done. The subdistributor then receives the gateways with the other networks and also includes the repeaters of the building network and concentrators. The physical transmission links are installed between the subdistributors and the offices. Naturally, a plurality of subdistributors may be connected among one another to the general distributor.
Increasingly often, the physical transmission links are made up of optical fibers, which enable extremely high transmission rates, up to one or more hundred megabits (Mbits) per second, while maximally limiting line losses.
Prewired building networks using any of the physical transmission carriers discussed above are described in more detail for instance in the commercial brochures, put out by the Bull Corporation, on the Bull Cabling System (BCS), a cabled network commercial sold by Bull. In each office, a certain number of connection outlets is fixed to the baseboard of walls, located in the lower portion of the walls closest to the floor, the outlets being intended to connect the cords from the terminal or terminals installed in each of bureaus.
When the local area network uses a transmission carrier made up of optical fiber cables, the wall outlets are optical connection outlets (the term "optical wall access point" is also used).
In current practice, optical prewiring of buildings involves practically only the main skeleton of the wiring and does not extend to the level of the offices, for reasons of customer needs and the cost of this prewiring. Nevertheless, a certain number of manufacturers and customers are interested in wall connection outlets, and one may expect that in the next few years, the technique of developing optical wall connection outlets will gain increasing success.
An optical wall connection outlet preferably has the following characteristics:
a relatively low cost; and PA1 capable of being prewired or postwired; PA1 it should be capable of being installed on demand, PA1 should be capable of being moved around, PA1 must be capable of being installed, or removed, very quickly, PA1 should not require particular tools to be installed, PA1 should enable very simply coiling up a certain length of optical cable without excessive strain on the cable, and if possible inside the baseboard; in particular, it must take into account the maximum radius of curvature that a cord of optical fiber can undergo so that it can be coiled without being damaged, PA1 finally, it should have a low cost. PA1 it should enable a user to be connected rapidly; PA1 it should enable simple coiling of a certain length of cable without excessive strain on it; and PA1 it should have a very low cost before use, with the prewiring access point being standardized. PA1 they do not generally accept more than a single type of connection; PA1 the direction in which the cords in use exit, toward the terminal or the station, is fixed; PA1 the wall outlet installed, in the case of prewiring, is cumbersome and this is true even if it remains unused thereafter, because it is systematically equipped with its connectors; and PA1 finally, it has only a single function: To connect the station or terminal to the incoming cable from the subdistributor. PA1 a receptacle adapted to be fixed in the baseboard of the wall, into which receptacle the optical cords carrying the information to be transmitted to the local area network of the building including a plurality of terminals are inserted, PA1 and means for connecting the cords to the terminal associated with the outlet, is characterized in that the connection means include: PA1 a removable cover associated with a removable carrier of connectors that facilitates the optical connection of said cords,
in postwiring,
In prewiring, the qualities desired for an optical wall connection outlet are as follows:
Moreover, in either case (postwiring or prewiring), the wall outlet must have a standard format, that is, the shape of a mosaic 50.times.50 mm in size, or optionally 45.times.45 mm, which will be the standard used in coming years. In addition, the optical wall connection outlet must be capable of accepting all types of connector.
In general, existing optical wall connection outlets are in the following form, described in conjunction with FIGS. 1a and 1b.
In FIG. 1a, a wall outlet of a first type, PM.sub.1 is seen, which is made up of a mosaic MOS.sub.1 of rectangular parallelepiped form fixed to the baseboard PL of the wall, the wall not being shown for the sake of simplicity in the drawing. The outlet PM.sub.1 also includes two connection plugs F.sub.1, F.sub.2 which are perpendicular to the front face FAV.sub.1 of the mosaic, the plane of which front face is parallel to the plane of the wall. The connection plugs F.sub.1 and F.sub.2 in fact have an oblong shape, and the language is misused when it is said they are perpendicular to the front face FAV.sub.1, when in fact it is their axis of longitudinal symmetry that is perpendicular to the surface of the wall, which is perpendicular to this front face. In FIG. 1a, two optical fibers cords C.sub.1, C.sub.2 are also seen, connected to the two plugs F.sub.1 and F.sub.2, respectively. To accomplish this, the two cords, which as shown in this same drawing figure arrive parallel to the wall and to the surface of the floor PLA must be bent to be connected to the two plugs F.sub.1 and F.sub.2 over an extremely short distance, so that these cords C.sub.1 and C.sub.2 do not have a insignificant radius of curvature R. As a result, it is difficult to coil the cable inside the baseboard in the vicinity of the plugs F.sub.1 and F.sub.2. In the case of the wall outlet PM.sub.1, the connection of the connection cords of the terminal is done in place.
Moreover, the wall outlets of the prior art have the following disadvantages:
Turning now to FIG. 1b, a wall outlet PM.sub.2 is shown which includes a mosaic MOS.sub.2 with a front face FAV.sub.2 having the same parallelepiped rectangular form as MOS.sub.1 and fixed to the baseboard PL in the same way. This wall outlet PM.sub.2 includes two connection plugs F.sub.3 and F.sub.4, which are perpendicular to the surface of the floor PLA and are accordingly oriented downward. In this same drawing, one can also seen the connection cords C.sub.3 and C.sub.4 connected to the plugs F.sub.3 and F.sub.4, and one can observe the presence of a not-insignificant radius of curvature R, which is made necessary to enable connection of the two cords to the two outlets. The disadvantage of the outlet PM.sub.2 is accordingly the same as for the outlet PM.sub.1, that is, the difficulty of coiling up cable to connect it to the two connection plugs F.sub.3, F.sub.4. These problems of the radius of curvature and of cable coiling are even more tricky to solve than in the case of the plugs shown in PM.sub.1. On the other hand, this installation, with connection plugs oriented downward in the mosaic, prevents all the dust located in great amounts on the floor of the office from collecting on the plugs.
The outlets PM.sub.1 and PM.sub.2 practically require prewiring and preconnectorization (with the plugs F.sub.1 -F.sub.2 or F.sub.3 -F.sub.4). This assumes that the problem of the radius of curvature and coiling of the fiber is mastered. The present invention makes it possible to overcome these problems while meeting all the characteristics and qualities described above.